The present invention generally relates to electromechanical devices. More particularly, this invention relates to electromechanical devices and electromechanical device-based modules, systems, and methods capable of monitoring environmental conditions, such as physical, electromagnetic, thermal, and/or chemical parameters within an environment.
Wireless sensors are employed in a wide range of applications including supply-chain and logistics, industrial and structural monitoring, healthcare, homeland security, and defense. Such sensors used as nodes of wireless networks are capable of high reliability, efficiency, and performance and enable ambient intelligence, total visibility, and smart adaptive systems. Generally, it is desired to minimize the power dissipation, size, and cost of wireless sensors by minimizing their power requirements. Wireless sensors can be equipped with integrated miniature batteries or capacitors as a dedicated on-board power source, as well as configured for operation without a power storage device. In many applications, batteryless operation may be preferred or required due to lack of battery replacement feasibility or stringent cost, form factor, and lifetime requirements. One approach to address this need is scavenging energy from environmental sources such as ambient heat, radio and magnetic waves, vibrations, and light, provided that at least one of these parameters is adequately available. Another approach is to remotely power a sensor by inductive or electromagnetic coupling, in which case energy may be optionally stored on an integrated capacitor so that sensor operation may occur over a short period of time prior to the capacitor becoming completely discharged. Finally, there are sensors that do not need any external energy source for sensing because they operate based on chemical reactions or mechanical events resulting in a color change or another change in their properties that can be detected by visual inspection or with use of an electronic detection system. The latter types of wireless sensors are generally in the form of sensor labels and do not readily lend themselves to automation.
U.S. Pat. Nos. 7,495,368, 7,619,346, 7,827,660, 7,907,037, 8,487,508, and 8,677,802 and U.S. Patent Application Publication No. 2011/0009773 disclose the use of arrays of digital micro-electro-mechanical-system (MEMS) sensing devices that can be manufactured and packaged at wafer-level with integrated circuits to yield a sensing module. Sensing devices within an array can be configured to respond to different levels of an environmental condition or parameter to enable the module to cumulatively measure the environmental condition.